In arterial bypass procedures and hemodialysis vascular access, there is a need for vascular grafts. However, autologous vessels are not always available due to previous harvesting or pre-existent vascular disease, and synthetic vessels often have poor patency rates due to infection, stenosis and thrombosis.
Therefore, recent approaches are aimed to provide for a completely biological blood vessel, for example via in vitro methods, with the use of scaffolds that are replaced by host cells and matrix over time, or by means of in situ vascular tissue engineering.
In situ vascular tissue engineering was first proposed in the seventies of the twentieth century, using a so-called Sparks mandrill to generate a tissue capsule that was formed around a porous Dacron mesh (Sparks 1969 Ann Thorac Surg August; 8(2):104-13; Sparks 1970 Ann Surg November; 172(5):787-94). This mandrill was implanted for several months in the muscle. However, the grafts largely failed due to thrombosis and aneurysm formation (Hallin 1975 Ann Surg September; 41(9):550-4; Hallin and Sweetman 1976 Am J Surg August; 132(2):221-3; Roberts and Hopkinson 1977 Nov. 5; 2(6096):1190-1).
Other groups have also studied an in situ tissue engineering approach, but using the peritoneum (Campbell et al 1999 Circ Res December 3; 85(12):1173-8) or the subcutaneous pouch (Sakai et al 2009 J of Biomedical Materials Research Part B: Applied Biomaterials: Vol90B(1): 412-410; Watanabe et al 2011 J of Biomedical Materials Research B: Applied Biomaterials Vol90B(1): 120-126) as bioreactor. However, intraperitoneal implantation and the subsequent harvesting are rather invasive and incur the risk of adhesion formation, possibly hindering successful clinical implementation. Moreover, not all implants become encapsulated (Campbell et al 1999 Circ Res December 3; 85(12):1173-8), creating the necessity to implant several devices. The approach of Sakai and Watanabe also leaves room for optimization of e.g. the implants and the characteristics of the generated tissue.
The present disclosure circumvents and/or solves some of the problems associated with earlier approaches and aims for improved methods for in situ tissue engineering, in particular in situ vascular tissue engineering.